1. Field of the Invention
The present invention relates to an emergency resuscitation apparatus and, more particularly, to an endoesophageal airway for emergency resuscitation, used for trying artificial respiration on an emergency patient in a critical condition, while providing an artificial passage for flow of air or oxygen to the lungs of the patient.
2. Description of the Prior Art
Up to now, artificial respiration has been employed widely to resuscitate an emergency patient in a critical condition. In the most case, this is carried out by endotracheal intubation in which an endotracheal tube is inserted into the trachea of the patient through the mouth or nose of the patient and then connected to a resuscitator to introduce air or oxygen into the patient.
In the endotracheal intubation, it is primarily required to insert a laryngoscope into the cavity of the mouth to visualize the larynx. Then, a distal end of the endotracheal tube must be inserted into the trachea quickly, while observing the glottis under direct laryngoscopy. Thus, there are only limited skilled persons who can practice sufficiently controlled artificial lung ventilation by the endotracheal intubation. In fact, in a certain country, the persons qualified to practice the endotracheal intubation have been limited to those licensed to practice such medical treatments, for example, medical doctors. Further, the endotracheal intubation involves technical difficulties when it is difficult to open the mouth of the patient or when the extension of the injured cervical spines endangers the patient in cases of cranial and cervical trauma. Since the regions between the innermost depths of the pharynx and the larynx have high risks of causing nervous reflexes, there is a great danger that the endotracheal intubation provides side effects such as arrhythmia, cardiac arrest, vomiting, laryngeal spasm, or the like when applied to a serious case whose respiratory function has been stopped.
In addition, the ciliated epitheliums of the trachea are very fragile to trauma or stresses. For example, they are weak in resistance to a pressure applied by a tube, a cuff, or a balloon, or get burnt easily by inhalation of hot air at a fire. Recently, therefore, there is a growing tendency to avoid breathing controls accomplished by inserting foreign substances into such delicate and fragile tracheae for a long time of period, as much as possible.
Recently, it has been proposed to use an esophageal obstructor airway (EOA) because of the fact that a respiration tube closed at one end will in all probability be introduced into the esophagus through the pharynx by inserting it blindly through the mouth of the patient along a median line without performing overextension of the larynx. The esophageal obstructor airways (EOA) are now employed in some countries including the United States of America, Canada and Japan as an emergency resuscitation apparatus. Such an apparatus generally comprises a respiration tube having a closed distal end and a proximal open end and being provided with air holes in a middle part of a side wall thereof, an inflatable balloon arranged near the distal end of the respiration tube, a slender elongated inflation tube connected to the inflatable balloon, and a face mask fixed to the open end of the respiration tube.
The artificial lung ventilation is carried out in the following manner: Firstly, the distal end of the respiration tube is inserted into the low esophagus of a patient through the mouth. Then, the inflatable balloon is inflated by supplying air through the inflation tube to bring it into close contact with the esophageal wall, and the face-mask is brought into close contact with the face of the patient. The open end of the respiration tube is connected to a lung ventilator or a resuscitator to practice positive pressure artificial respiration on the patient. The air fed to EOA flows out of the respiration tube into the trachea through the air holes. Since the esophagus is blocked by the balloon, the air does not flows into the stomach, but flows into the trachea via the pharynx and glottis, and then into the lungs of the patient. The air in the lungs is then exhaled in the reversed course by releasing the pressure. This process ensures easy and rapid intubation, but it has to be assisted by an assistant to hold the mask in close contact with the face of the patient. In addition, a location of the distal end of the respiration tube put in the esophagus cannot be adjusted at will, sometimes resulting in failure in obstruction by the inflated balloon. Further, it is difficult to hold close contact between the mask and the face of the patient during transport within an ambulance.
On the other hand, there have been used laryngeal mask airways (LMA) imported from the United Kingdom, which has a structure as shown in FIG. 5. Such a laryngeal mask airway comprises a hollow respiration tube 101 like a short endotracheal tube, a cushion mask 102 mounted on one open end of the tube 101 and having an inflatable ring-like cushion 103 attached thereto, and means 105 for inflating the ring-like cushion 103. In use, the cushion 103 is deflated to minimize its volume and then inserted from the cavity of the mouth toward the larynx along the median line until the cushion 103 is stopped around the area between the pharynx and larynx. In this position, the cushion 103 is inflated by introducing a certain amount of air through the inflating means 105 and brought into close contact with the laryngeal opening, thereby closing the uppermost part of the esophagus and preventing the flow of air into the stomach. Under such a condition, the positive pressure artificial lung ventilation is accomplished through the opposite open end 104 of the respiration tube 101.
The intubation of LMA can be carried out with ease and rapidly when the patient is under anesthesia or unconsciousness. Also, if it is easy to open the mouth of the patient because of deep anesthesia, and if the patient shows no local nervous reflex but has any spontaneous respiration, it is easy to perform the proper intubation as the respiration tube can be thrust properly by confirming the location of the distal end thereof with the breath sounds through it.
However, such an apparatus involves technical difficulties for use in emergency resuscitation. For example, it is difficult to locate the respiration tube on the proper position rapidly when the respiratory function of the patient has been stopped for some reason or other. Further, there is a fear of blockage of the airway when the cushion is inflated greatly. In addition, it is difficult to bring the cushion into close contact with the laryngeal opening because of a complex configuration of the pharynx. In case of the high positive pressure artificial ventilation, the cushion can not be brought into close contact with the laryngeal opening, thus making it difficult to prevent the flow of air into the stomach, which in turn results in failure in artificial lung ventilation.